1. Field of the Invention
The present invention relates to a system and method for providing triggered location information. More particularly, the present invention relates to a Secure User Plane Location (SUPL), which is under discussion in a Location (LOC) group, one of the working groups belonging to the Open Mobile Alliance (OMA) standard organization.
2. Description of the Related Art
FIG. 1 is a diagram illustrating a signal flow for a conventional triggered location request service defined in the SUPL 2.0 standard, the entire disclosure of which is hereby incorporated by reference.
A location information providing system using the SUPL 2.0 standard includes a SUPL Agent 104 for requesting a location of a target SUPL-Enabled Terminal (target SET) 102, a Home-SUPL Location Platform (H-SLP) 100 which is requested by the SUPL Agent 104 to provide the location information of the target SET 102 and performs a positioning process together with the target SET 102, and the target SET 102 which is a target of the request for the location information.
When the SUPL Agent 104 desires to know a location of the target SET 102, whenever a preset condition is satisfied, the SUPL Agent 104 transmits a Mobile Location Protocol Triggered Location Reporting Request (MLP TLRR) message to the H-SLP 100 in step 106. The MLP TLRR message includes an ID (client-id) of the SUPL Agent 104, an ID (msid) of the target SET 102, a service initiation time, a service end time, location information transmission conditions, etc. Herein, if a location of the target SET 102 is provided at every preset period of time (periodic trigger), the location information transmission condition corresponds to a time. If a location of the target SET 102 is provided whenever a specific event occurs (event trigger), the location information transmission condition corresponds to a specific event occurrence condition.
When receiving the MLP TLRR message, the H-SLP 100 performs an authentication process of the SUPL Agent 104. When the H-SLP 100 determines that the SUPL Agent 104 has been authorized to get a location value of the target SET 102, the H-SLP 100 determines routing information of the target SET 102 in step 108. That is, the H-SLP 100 determines if the target SET 102 is in a roaming state and if the target SET 102 can support a SUPL protocol. Herein, it is assumed that the target SET 102 is in a non-roaming state. When it is determined that the target SET 102 is in the non-roaming state and supports the SUPL protocol, the H-SLP 100 transmits a SUPL INIT message to the target SET 102 in step 110. When receiving the SUPL INIT message, the target SET 102 enables a data connection with the H-SLP 100 in step 112.
After the data connection is established, the target SET 102 examines currently supportable positioning capabilities (SET capabilities) in step 113 and transmits a SUPL TRIGGERED START message, including the SET capabilities, to the H-SLP 100 in step 114. That is, the SUPL TRIGGERED START message contains SET capabilities' parameters which include information about a protocol and a positioning method supportable by the target SET 102. When receiving the SUPL TRIGGERED START message, the H-SLP 100 determines a positioning method by using the SET capabilities in step 115, and then transmits a SUPL TRIGGERED RESPONSE message, including the determined positioning method, to the target SET 102 in step 116.
When receiving the SUPL TRIGGERED RESPONSE message, the target SET 102 stores the determined positioning method in a memory in step 117. Then, the H-SLP 100 transmits a Mobile Location Protocol Triggered Location Reporting Acquisition (MLP TLRA) message to the SUPL Agent 104 to notify that the triggered location request service has been accepted in step 118.
After the H-SLP 100 reports that the triggered location request service has been accepted, the data network access between the H-SLP 100 and the target SET 102 is terminated. Thereafter, the target SET 102 determines if a location information transmission condition is satisfied in step 120. When the location information transmission condition is not satisfied, the target SET 102 is maintained in the current state. In contrast, when the location information transmission condition is satisfied, the target SET 102 transmits a SUPL POS INIT message to the H-SLP 100 to report an initiation of the positioning in step 122. When the SUPL POS INIT message has been received, the data network access is established between the H-SLP 100 and the target SET 102, and a SUPL POS session process is performed between the H-SLP 100 and the target SET 102 according to the determined positioning method in step 124.
When the calculation of a location value has been finished in the SUPL POS session process of step 124, the H-SLP 100 transmits the location value of the target SET 102 to the SUPL Agent 104 through a Mobile Location Protocol Triggered Location Report (MLP TLREP) message in step 126. After the location value of the target SET 102 is transmitted to the SUPL Agent 104, the data network access between the H-SLP 100 and the target SET 102 is terminated, and the target SET 102 again determines if the location information transmission condition is satisfied in step 120. Steps 120 to 126 are repeatedly performed until a service end time.
As described above, according to the triggered location request service, whenever the location information transmission condition is satisfied, the positioning process is performed between the H-SLP 100 and the target SET 102, and a location value obtained through the calculation process is transmitted to the SUPL Agent 104. When the location information transmission condition is satisfied, the target SET 102 transmits a SUPL POS INIT message to the H-SLP 100, wherein the SUPL POS INIT message includes the positioning capabilities (SET capabilities) of the target SET 102. However, the SET capabilities according to the conventional triggered location request service contain only information about types of positioning modules (e.g. A-GPS, TDOA, etc.) included in the target SET 102, and does not contain any information about whether or not each positioning module is actually operating. This is because only an immediate location request service where a location value is calculated is only considered once in the SUPL 1.0 standard. That is, the immediate location request service has been designed with the idea that merely reporting information about what types of positioning modules are in the target SET 102 would be sufficient. However, this is based on the assumption that most of positioning modules in the target SET 102 are operating. Such an idea is reflected, even in a SUPL 2.0 standard, that proposes the triggered location request service, without any change.
In contrast to the immediate location request service of the SUPL 1.0 standard in which a location value is calculated only once, the triggered location request service is a service for calculating a location value of the target SET 102 over a long period of time, so that a situation of the target SET 102 may be changed during a service period. That is, for example, the target SET 102 may move to an area where a GPS signal cannot be received while the location of the target SET 102 is being calculated by using GPS, and the target SET 102 may receive signals from three or less adjacent cells while the location of the target SET 102 is being calculated by using Time Difference Of Arrival (TDOA).
In this case, the H-SLP 100 performs a SUPL POS session process without recognizing the current situation of the target SET 102, and therefore, cannot recognize that it is not possible to calculate the location of the target SET 102 until the SUPL POS process is performed. However, since the H-SLP 100 cannot still recognize the current situation of the target SET 102, the H-SLP 100 re-performs a SUPL POS session process, and transmits an error message to the SUPL Agent 104 after it has been continuously subjected to a failure in the positioning for a preset period of time. Therefore, when the positioning is not possible, the SUPL Agent 104 may wait for a location service for a long time despite the SUPL Agent 104 not being able to receive any location information in the end.
Further, when the target SET 102 has two or more positioning modules, the H-SLP 100 first uses a first positioning method having the highest priority, and then uses a second positioning method when it is not possible to use the first positioning method. Therefore, when it is not possible to use the positioning method having the highest priority, it may take too much time until the user of the SUPL Agent 104 receives a location service.